If using fresh udon, gently separate them in warm water. If using frozen, boil for 1-2 minutes until loosened, then drain.
Make the sauce
In a small bowl, whisk together soy sauce, hoisin sauce, gochujang, honey, rice vinegar, and sesame oil. Set aside.
Cook the pork
Heat oil in a large skillet or wok over medium-high heat. Add the sliced pork and stir-fry until browned and slightly crispy, about 5 minutes.
Sauté the aromatics
Add the onion, bell pepper, garlic, and ginger. Stir-fry for 3 minutes until softened.
Toss in the noodles
Add the udon noodles and the sauce to the pan, tossing everything together until the noodles are well coated and heated through. Let it cook for another 2 minutes.
Finish & Serve
Remove from heat and garnish with green onions and sesame seeds. Serve immediately!